Dewpoint cooler designed as a frame or part thereof

ABSTRACT

A dewpoint cooler comprises: a first air circuit and a second air circuit coupled thereto via a heat-conducting wall, through which two circuits can flow two media, wherein the second medium contains a gas, heat-conducting wall break-up means for breaking up at least the thermal boundary layer ( 50 ), the laminar boundary layer and the relative humidity boundary layer in both media, which break-up means comprise heat-conducting protrusions; wherein the surfaces of said wall and the break-up means are covered with a hydrophilic coating, which can absorb an evaporable liquid, retain it and relinquish it again ( 100 ), such that the wetted coating, the heat-conducting surfaces and the break-up means are cooled. A wetting ( 150 ) unit for subjecting the secondary medium to wetting by the evaporable liquid such that evaporated liquid entrained by the secondary medium extracts heat from the primary medium via the wall.

The invention relates to a dewpoint cooler, comprising: a first aircircuit and a second air circuit thermally coupled thereto via an atleast partially heat-conducting wall, through which two circuits canflow two respective media, wherein at least the second medium contains agas, for instance air, with a relative humidity of less than 100%; whichheat-conducting wall has break-up means such as fins for breaking up atleast the thermal boundary layer, the laminar boundary layer and therelative humidity boundary layer at the position of at least activezones in both media for heat transfer, which break-up means compriseheat-conducting protrusions which enlarge the effective heat-conductingsurface area of said wall; wherein the heat-conducting surfaces of saidwall and the break-up means are at least partially covered at least inthe area of the secondary medium with a hydrophilic, for instancehygroscopic coating, which coating is for instance porous and/or canabsorb water by capillary action, retain it and relinquish it againthrough evaporation, such that the wetted coating, and thereby also theheat-conducting surfaces and the break-up means, are cooled; primarydrive means based on pressure difference, for instance a fan or pump,for the primary medium; secondary drive means based on pressuredifference, for instance a fan, for the secondary medium; and a wettingunit for subjecting the secondary medium to wetting by the water byevaporating liquid from the coating such that the evaporated liquidentrained by the secondary medium extracts heat from the primary mediumvia the heat-conducting wall.

Such a dewpoint cooler is known.

The known dewpoint coolers are standalone devices generally having aform and dimensions which from an aesthetic viewpoint often leavesomething to be desired in an interior.

In this respect it is an object of the invention to provide a dewpointcooler which is wholly integrated into the architectural structure of abuilding, and which is therefore practically invisible.

In this context the dewpoint cooler according to the invention ischaracterized by a housing in which the walls bounding the air circuitsare accommodated, which housing is adapted as border or frame, or a partthereof, for an outside door or outside window of a building, whereinthe inlet of the primary circuit and the outlet of the secondary circuitare situated on the outside and the outlet of the primary circuit andthe inlet of the secondary circuit are situated on the inside.

The dewpoint cooler according to the invention is preferably embodiedsuch that the coating consists of a porous technical ceramic material,for instance a burnt layer, a cement such as a Portland cement, or afibrous material, for instance a mineral wool such as rockwool. Withsuch a coating it is possible to achieve that the liquid applied to thecoating by the wetting unit spreads rapidly in the coating while thecoating has a substantial buffering capacity for the water.

It is important that the coating has a small thickness, for instance inthe order of 50-100 Hm, such that the thermal resistance caused in thecoating by the water is very small.

In a preferred embodiment the dewpoint cooler according to the inventionhas a reversing unit for reversing a part of the primary airflow at theoutlet of the first air circuit in order to form the secondary airflow,wherein the primary drive means are also the secondary drive means.

The secondary airflow can for instance amount to about 30% of theintroduced primary airflow, whereby the secondary airflow carried to thespace for cooling then amounts to about 70% of the introduced primaryairflow.

In a particular embodiment the dewpoint cooler can have the specialfeature that the reversing unit can be switched off such that the twoairflows can be separated and the wetting means can be switched off,this such that the dewpoint cooler can operate as heat exchanger forrecovering heat discharged to the outside by the secondary airflowthrough transfer of heat in the heat exchanger to the primary airflow.

In the summer for instance the dewpoint cooler can thus operateeffectively as dewpoint cooler, while in the winter it operates asheat-recovering heat exchanger.

In yet another embodiment the dewpoint cooler has the special featurethat the ratio between the primary airflow and the secondary airflow canbe adjusted by means of adjusting means such that the efficiency of thedewpoint cooler is adjustable.

With such an embodiment it is possible to vary from the ratio of 30:70stated above by way of example between the secondary cooling airflow andthe cooled airflow supplied to the space. The optimization can takeplace with control means such that the dewpoint can be approached withina very small margin, for instance 1 C.

This latter variant can be embodied such that the adjusting means areembodied as an optionally adjustable through-feed in the primary circuitand an adjustable through-feed in the secondary circuit.

Alternatively, use can also be made of two separated fans forrespectively the primary airflow and the secondary airflow.

A specific embodiment has the special feature that the fans are at leastpartly powered by a rechargeable battery which is charged by a solarpanel collecting sunlight from the outside. Depending on the expectedsunshine, the power supply from the rechargeable battery can be furtherassisted by additional mains supply.

The dewpoint cooler according to the invention can be further embodiedsuch that it can be coupled in modular manner to a similar dewpointcooler, for instance at an angle of 90.

The fans can for instance be supplied as separate blocks such that, whena number of dewpoint coolers according to the invention are coupled, useneed only be made of a total of two fans.

The invention also relates to a building with at least one door and/orone window with a frame.

This building has the feature according to the invention that at leastone of the borders of this frame is embodied as a dewpoint cooler inaccordance with the above stated specifications.

The dewpoint cooler according to the invention is very cheap tomanufacture and install, and combines the function of window frame withthat of dewpoint cooler. The invention is therefore very practical whenthere is shortage of space.

The dewpoint cooler is further always embodied as independent orstandalone unit, whereby it is possible to dispense with lines, cablesand the like. A simple mains cable may well be necessary for powersupply to the fans.

When old buildings are renovated the dewpoint cooler according to theinvention can be utilized very successfully.

When frames are replaced, parts thereof, or at least specific borders,can be embodied as dewpoint coolers according to the invention. In thiscase it is also possible to dispense with the installation of expensiveair-conditioning systems.

In buildings the concept of double flux and single flux is used in thecase of a controlled ventilation. With a double flux there is a completecontrol of both the incoming and outgoing airflow. This is for instancethe case in a dewpoint cooler, whether or not it be of the typeaccording to the invention, wherein the building is hermetically sealedapart from the dewpoint cooler. In the case of a single flux there is aventilation flow to the outside, wherein gaps, chinks and cracks providethe introduced air.

Window and door frames consist of a frame with profiles in aluminium,PVC, steel, wood or combinations thereof.

The dewpoint cooler according to the invention can be used in differentpositions. For an outside wall it can be vertical, in a pitched roof itcan be arranged obliquely, in a horizontal roof it can be placedhorizontally.

The dewpoint cooler according to the invention can be embodied asbuilt-in border or surface-mounted border.

The housing can for instance be designed such that the dewpoint coolerfits therein by means of a snap system. The same applies for filterswhich may be applied for the primary and secondary airflow.

The dewpoint cooler according to the invention can be applied in anydesired position and on any edge of a door or window. The following fouroptions are particularly important:—heat exchanger air/air, doubleflux—dewpoint cooler, single flux—dewpoint cooler, double flux—thecombination of heat exchanger air/air, single or double flux.

It should be appreciated that the dewpoint cooler according to theinvention can be a fully standalone unit and requires no coupling toother systems.

The airflow rate in both the primary and secondary circuits ispreferably a minimum of 6 m3/h, but the flow rate can also be greater inaccordance with the wishes of the user and the application. It is alsonecessary to consider whether the air-conditioning is total or partial.

The dewpoint cooler according to the invention can be embodied in doubleflux with equal flow rates, but also with different flow rates. In thismanner the possibility can readily be created of ventilating forinstance sanitary spaces with single flux.

Reference is made by way of example to the possibility of two rooms in abuilding being supplied from outside with 60 m3/h (primary circuit)while 50 m3/h is discharged. There then remains a surplus of 10 m3/h.Two rooms therefore give a surplus of 20 m3/h. By way of for instancecracks or holes in the door of a sanitary space this flow of 20 m3/h canbe discharged to the outside by means of an additional sanitary spacefan.

The dewpoint cooler according to the invention can also function as heatrecovery heat exchanger by optionally reversing the fans or making useof a built-in automatic or controlled valve.

It will be apparent that the dewpoint cooler itself must be practicallysilent, for instance may not produce more noise than 38 dB (A) at adistance of 1 m.

In addition, the dewpoint cooler may only have a negligible soundtransmission.

The dewpoint cooler may not, particularly in a gale, produce any noisenuisance in the form of whistling, sighing, rattling and so on.

Power supply preferably takes place at a maximum voltage of 48V directcurrent or alternating current. Below this value there is no specificsafety norm in force, and low-voltage connecting means can be used, forinstance mini-socket outlets.

These socket outlets can be important for, among others, the followingaspects: power supply to the fans and possible electronic control means,remote control, adjustment, failure report or report of the measure offouling, central closing in the case a stench wave occurs, centralclosing in the case a fire protection becomes operative, connection tobuildings, management centre, burglar alarm and a frequency controlsystem, which can optionally also be driven wirelessly. In the lattercase it is possible to largely dispense with the use of lines, whichwill stimulate the standalone character of the dewpoint cooler accordingto the invention.

It is important to provide the dewpoint cooler with filters. On the onehand this is to prevent fouling of the dewpoint cooler itself, whichcould have an adverse effect on the heat transfer, on the other hand toprevent floating dirt and dust being carried for instance from outsideto the inside and, conversely, from inside to the outside. The filterscan be of per se known type and can preferably be embodied in the formof insert units such that they are easily replaceable.

In the case of a dewpoint cooler of the type according to the inventionwhich is installed on a window frame, the operation of the fans has tobe stopped at the moment the window is opened. A built-in magneticcontact can for instance be used for this purpose.

Use can further be made of a failure reporting means, for instancerelating to the operation of the fans and possible fouling of thefilters and the heat-exchanging surfaces.

Simple computer fans with low flow rate can be used as fans. A fan witha relatively high rotation speed can also be applied. As alternative itis possible to envisage the use of one drive motor with two fan blades,one for the primary circuit and one for the secondary circuit.

A bypass valve can be used for switching between winter operation withheat exchanger and summer operation without heat exchanger. Inair-conditioning applications the heat exchanger is always used. Abypass valve is also suitable for preventing icing up. The bypass valvecan be controlled for hand-operated or automatic deicing. During thefree cooling period, particularly at nighttime, fresh outside air can becarried inside without heat exchange. This can optionally take place atan increased airflow rate, which will possibly be accompanied by aslightly increased noise production.

When two fans are used in the dewpoint cooler according to theinvention, both circuits can then be used for this ventilation. Anoverpressure-relief valve can optionally be arranged elsewhere in theventilated space for this purpose.

In the case of gale or other dramatic overpressure conditions, use canfor instance be made of a non-return valve in the form of an air valveor the like. A very quickly responding air valve can for instance bebased on the use of a table-tennis ball. Use can also be made of aprotective plate to prevent the inlet and outlet being directlyinfluenced on the outside. An air valve can also be based on a rubberbellows or other type of valve.

Protection against rainwater can take place with per se known protectivemeasures, particularly covers.

Covering by curtains on the inside of a window with dewpoint coolersaccording to the invention in the vertical borders can be prevented bydirecting the blown-out airflow obliquely inward instead ofperpendicularly of the main plane of the window. This prevents thecurtains flapping too much.

The air from outside is also prevented from being blown inwardineffectively. Use can be made of one or more nozzles with adjustableangle. The flow rate of the airflow is also kept relatively low so as toprevent an undesirable increase in the k-factor of the pane in question.

Radiators are often placed under a window. In such a situation it isdesirable to have the air discharge take place on the upper border.There is otherwise the danger of warm air from the radiator being drawnoff.

When curtains are closed the air discharge must remove the air from theroom. Account must therefore be taken of curtains in the placing ofinlets and outlets. In the case of office buildings, where curtains arenot usually applied, nozzles driven in oscillating manner can also beapplied, whereby the air in question is properly spread through thespace.

The invention will now be elucidated with reference to the annexeddrawings of a random embodiment. In the drawings:

FIG. 1 shows a partly cut-away perspective view of a known dewpointcooler;

FIG. 2 shows a longitudinal section through the dewpoint cooler of FIG.1;

FIG. 3 shows a perspective view, partly drawn in exploded view, of aframe with the dewpoint cooler according to FIGS. 1 and 2;

FIG. 4 shows a view corresponding with FIG. 1 of the dewpoint cooleraccording to the invention;

FIG. 5 shows a view corresponding with FIG. 2 of the dewpoint cooleraccording to the invention; and

FIG. 6 shows a view corresponding with FIG. 2 of an alternative dewpointcooler according to the invention.

FIG. 1 shows a dewpoint cooler 1 embodied in this embodiment as heatexchanger, i.e. without wetting means, whereby the heat exchanger couldoperate according to the invention as dewpoint cooler.

Dewpoint cooler 1 comprises two very schematically shown sets of airthrough-flow channels which form respectively a primary circuit I and asecondary circuit II, through which two airflows 2 and 3 respectivelycan flow in heat-exchanging contact to be described hereinbelow. Betweenthe channels drawn in this case as being single, generally the circuitsI and II, is situated a heat-conducting wall 4 on which symbolicallydesignated fins 5,6 are placed respectively in primary circuit I andsecondary circuit II. These fins are manufactured for instance fromcopper and increase the effective heat-exchanging capacity of wall 4considerably.

A housing 26 bounds the dewpoint cooler and co-acts sealingly with wall4 such that circuits I and II are completely separated physically.

Housing 6 has four passages for the two circuits I, II, viz. inlet 7 ofthe primary circuit, outlet 8 of the primary circuit, inlet 9 of thesecondary circuit and outlet 10 of the secondary circuit. Passages 8 and9 are situated on the inside, thus in the space to be ventilated orconditioned, while passages 7,10 are situated on the outside, and arethus in contact with the ambient air.

A fan 11 is situated in circuit I; a fan 12 is situated in circuit II.as described above, the flow rates of flows 2 and 3 can be the same aseach other, but can also differ from each other in controlled mannersuch that a residual flow rate has to discharged or supplied elsewhere.

As FIG. 3 shows, dewpoint cooler 1 is embodied as the lower border of aframe 13 which forms the framework for a window pane 14. In a particularembodiment one or more of the remaining borders 13,15 can also beembodied as a dewpoint cooler according to the invention. These dewpointcoolers 6, 13,14 etc. can be coupled to each other in modular manner andfor instance have a number of passages and fans in common.

It is pointed out emphatically that the construction shown in FIG. 2 isonly very schematic and symbolic. A dewpoint cooler, or in the narrowsense a heat exchanger, will generally comprise a number ofheat-exchanging walls with fins combined into a package. This realpractical structure is omitted for the sake of clarity in the drawings.

Attention is further drawn to the fact that passages 8,9 and 10,7 do notnecessarily have to be placed adjacently of each other, but can also bearranged spaced apart from each other. There is a smaller risk hereby ofthe flows 2 and 3 influencing each other. This can also be realized byjet-streams or nozzles with an angle differing from the drawn angles,optionally adjustable.

The dewpoint cooler according to FIG. 1 further comprises a solar panel16 which can collect sunlight and convert it into electricity, which isused to charge a rechargeable battery (not shown) which is adapted tosupply power to fans 11,12 via electronic means. Solar panel isaccommodated in a protruding part 17 of housing 26, but can also formpart thereof. The unit 16,17 is not shown in FIGS. 2 and 3.

Fins 6 and the surface of wall 4 directed toward the secondary circuitII are preferably treated such that the relevant surfaces arehydrophilic. By making use of the wetting means an effective wettinghereby takes place which brings about a cooling effect when airflow 3 isguided therealong. Via the heat transfer to the other side of wall 4 andfins 5, this cooling effect is converted into a cooling of primaryairflow 2.

FIG. 4 shows a dewpoint cooler 41 according to the invention. Theexterior differs from the heat exchanger 1 of FIG. 1 in the sense thatit has only one outlet tube 8 on the inside of the building. This aspectwill be further elucidated with reference to FIG. 5. The appearance isotherwise identical to that of heat exchanger 1.

FIG. 5 shows very schematically the internal and functional structure ofdewpoint cooler 41. Downstream of fan 11 the primary airflow 2 is splitinto two partial flows, viz. the outgoing cooled airflow 2′ (forinstance 70% of airflow 2) and a second branched flow 2″ of cooling air(for instance 30% of airflow 2) which is guided through an opening 42.The through-feed of opening 42 relative to the through-feed of passage 8determines said ratio between flow rates 2″ and 2.

Not shown in the schematic view of FIG. 5 are the wetting means whichserve to feed water for evaporation directly to a coating on secondaryfins 6. This coating consists for instance of Portland cement with athickness of 70 Am. The water supplied by feed conduits from adispensing system makes the cement coating wet. The secondary airflow 3,which has a humidity of less than 100%, provides evaporation of thewater on the relevant surface, this water in the form of water vapour inthe secondary outlet airflow 3 being generated to the outside viaopening 10. The heat extracted from fins 6, and thereby wall 4, due tothe evaporation of the water is fed via fins 5 from the primary airflow2, which is thereby cooled.

FIG. 6 shows a hybrid embodiment of the dewpoint cooler according to theinvention. Other than dewpoint cooler 41, this dewpoint cooler 51 is notprovided with a fixed opening 42 downstream of fan 11, but with a valve43 which can be displaced by an actuator 44 between the first positionshown in full lines and the second position 43′ shown in broken lines.In position 43 the airflow 2 is generated directly to the inside viapassage 8, while in position 43′ the valve 43 leaves opening 42 clearand closes passage 9. The same function is then thus obtained as in FIG.5. In the first position the dewpoint cooler 51 can operate as heatexchanger for heat recovery. If desired, it could also function ascooler, although it is noted in this respect that in that case theability to control the mutual ratio of flows 2 and 3 is less good. Thisis a drawback in the case the best possible efficiency is desired.

It is further noted that in order to reduce noise production the fans11,12 can be spring mounted. Use can further be made of known acousticdamping means which can effectively reduce sound exiting via the housingand passages 8,9. In order to prevent resonance phenomena at therotation frequency of the fans, the housing 6 can be manufactured from amaterial which strong internal damping or be provided with a bituminousinner layer, or a large mass, and thus have a great wall thickness.

Attention is finally drawn to the fact that in the case of a differentplacing of the passages it may be necessary to apply interlacing unitsand manifolds connecting the diverse passages to the sets of channels.

1. Dewpoint cooler, comprising: a first air circuit and a second aircircuit thermally coupled thereto via an at least partiallyheat-conducting wall, through which two circuits can flow two respectivemedia, wherein at least the second medium contains a gas, for instanceair, with a relative humidity of less than 100%; which heat-conductingwall has break-up means such as fins for breaking up at least thethermal boundary layer, the laminar boundary layer and the relativehumidity boundary layer at the position of at least active zones in bothmedia for heat transfer, which break-up means comprise heat-conductingprotrusions which enlarge the effective heat-conducting surface area ofsaid wall; wherein the heat-conducting surfaces of said wall and thebreak-up means are at least partially covered at least in the area ofthe secondary medium with-a hydrophilic, for instance hygroscopiccoating, which coating is for instance porous and/or can absorb water bycapillary action, retain it and relinquish it again through evaporation,such that the wetted coating, and thereby also the heat-conductingsurfaces and the break-up means, are cooled; primary drive means basedon pressure difference, for instance a fan or pump, for the primarymedium; secondary drive means based on pressure difference, for instancea fan, for the secondary medium; and a wetting unit for subjecting thesecondary medium to wetting by the water by evaporating liquid from thecoating such that the evaporated liquid entrained by the secondarymedium extracts heat from the primary medium via the heat-conductingwall; characterized by a housing in which the walls bounding the aircircuits are accommodated, which housing is adapted as border or frame,or a part thereof, for an outside door or outside window of a building,wherein the inlet of the primary circuit and the outlet of the secondarycircuit are situated on the outside and the outlet of the primarycircuit and the inlet of the secondary circuit are situated on theinside.
 2. Dewpoint cooler as claimed in claim 1, wherein the coatingconsists of a porous technical ceramic material, for instance a burntlayer, a cement such as a Portland cement, or a fibrous material, forinstance a mineral wool such as rockwool.
 3. Dewpoint cooler as claimedin claim 1, comprising a reversing unit for reversing a part of theprimary airflow at the outlet of the first air circuit in order to formthe secondary airflow, wherein the primary drive means are also thesecondary drive means.
 4. Dewpoint cooler as claimed in claim 3, whereinthe reversing unit can be switched off such that the two airflows can beseparated and the wetting means can be switched off, this such that thedewpoint cooler can operate as heat exchanger for recovering heatdischarged to the outside by the secondary airflow through transfer ofheat in the heat exchanger to the primary airflow.
 5. Dewpoint cooler asclaimed in claim 3, wherein the ratio between the primary airflow andthe secondary airflow can be adjusted by means of adjusting means suchthat the efficiency of the dewpoint cooler is adjustable.
 6. Dewpointcooler as claimed in claim 5, wherein the adjusting means are embodiedas an optionally adjustable through-feed in the primary circuit and anadjustable through-feed in the secondary circuit.
 7. Dewpoint cooler asclaimed in claim 1, wherein the fans are at least partly powered by arechargeable battery which is charged by a solar panel collectingsunlight from the outside.
 8. Dewpoint cooler as claimed in claim 1,wherein a dewpoint cooler can be coupled in modular manner to a similardewpoint cooler, for instance at an angle of
 90. 9. Building with atleast one door and/or one window witha frame, characterized in that atleast one of the borders of this frame is embodied asa dewpoint cooleras claimed in any of the claims 1-8.